Field of the Invention
The present invention relates to a process for the preparation of asphalt-epoxy resin compositions which comprises mixing (a) a heated asphalt, with a composition comprising (b) an epoxy resin and (c) an amine having two active hydrogen atoms and either an aliphatic hydrocarbon group having 8 to 22 carbon atoms or an alkyl phenol group in which the alkyl group has 8 to 22 carbon atoms.
Ruts or waviness occur or other unwanted flows occur on the surfaces of asphalt pavements at points near intersections, on slopes, at sharp curves or on bridges constructed by using steel floor plates owing to the loads of automobiles and shear stresses caused by braking operations. Further, in snowy and cold areas, asphalt pavements are peeled off and worn away vigorously by snow tires or tire chains. These undesirable phenomena are due to the inherent property of asphalt, namely, a high temperature sensitivity, which means that its physical properties are easily changed depending on the temperature changes. For example, the temperature of the road surface can be as high as 60.degree. C. in summer, even though the softening point of asphalt is about 43.degree. C. Accordingly, in summer, loads of automobiles, especially static loads generated by stopping at points near intersections, readily cause rutting of pavements. Asphalt becomes hard as the ambient temperature becomes lower, and the Fraass breaking point of asphalt, at which asphalt is solidified like glass and is readily broken by a shock, is about -14.degree. C. In cold regions, the temperature of the road surface can be as low as about -20.degree. C. and shocks of a tire chain or the like can be imposed on the road surface. Accordingly, it is inevitable that the surfaces of pavements are readily broken and scattered by tire chains or snow tires in cold regions.
The composition of the present invention overcomes these defects of conventional road-paving asphalts. The composition of the present invention is especially effective for repairing existing roads at intersections, slopes or sharp curves at which rutting or waviness has already occurred. The reason is that the composition of the present invention satisfies an important requirement for the repair of roads, namely, that the time during which the road is blocked or closed while the repair is being done should be as short as possible. In the present invention, the amine acting as a curing agent for the epoxy resin has only two active hydrogen atoms for reacting with epoxy groups, and therefore, if a difunctional epoxy resin is used, a thermoplastic linear epoxy resin is readily formed. Accordingly, if the specific amine of the present invention and an epoxy resin are added to a heated asphalt, the reaction progresses rapidly thereby to increase the molecular weight of the epoxy resin, but since the resulting epoxy resin is thermoplastic, the heated asphalt-epoxy resin composition retains a liquid state. Therefore, an asphalt mixture including this asphalt-epoxy resin composition as a binder has a very good operational adaptability when used in the heated state, and when the temperature of the paving composition is lowered to ambient temperature, the mixture forms a pavement having a very high strength. Accordingly, when an asphalt mixture including the asphalt-epoxy resin composition prepared according to the process of the present invention is used for repairing roads, the road can be opened to traffic again after only a short time required for cooling of the repaired pavement, calculated from the completion of the paving treatment. For example, when the epoxy resin content is 40% by weight, the asphalt-epoxy resin composition according to the present invention has a softening point of 125.degree. C., a Fraass breaking point of -40.degree. C., a tensile strength of 22 Kg/cm.sup.2 and an elongation of 300%, although the values of these physical properties vary to some extent depending on the amount of the epoxy resin in the paving composition. Accordingly, it is expected that when the asphalt-epoxy resin composition according to the present invention is used for a paving operation, the resulting pavement will not become softened in summer and it will not be broken up or scattered by shocks of tire chains in winter. Moreover, the fact that the elongation is as high as 300% means that even if the substrate is an asphalt pavement or steel floor plate, the pavement made of the composition of the present invention can follow the bending or other deformation of the substrate.
In the present invention, as the amine having two active hydrogen atoms and either an aliphatic hydrocarbon group having 8 to 22 carbon atoms or an alkyl phenol group in which the alkyl group has 8 to 22 carbon atoms, there are preferably employed compounds having the following formula: EQU R--NH.sub.2 (I)
wherein R stands for an alkyl group having 8 to 22 carbon atoms or an alkenyl group having 8 to 22 carbon atoms, compounds having the following formula: EQU R'--O--A.sub.n --(CH.sub.2).sub.3 --NH.sub.2 (II)
wherein R' stands for an alkyl group having 8 to 22 carbon atoms or an alkenyl group having 8 to 22 carbon atoms, or an alkylphenyl group in which the alkyl group has 8 to 22 carbon atoms, A stands for an oxyethylene or oxypropylene group, and n is an integer of from 0 to 20, and compounds represented by the following general formula: EQU RNH--R.sub.1 --NH--B (III)
wherein R stands for an alkyl group having 8 to 22 carbon atoms or an alkenyl group having 8 to 22 carbon atoms, R.sub.1 stands for an alkylene group having 2 to 3 carbon atoms, and B stands for a group selected from the class consisting of hydroxyethyl, 1-hydroxy-2-methylethyl, 1-chloro-2-hydroxypropyl, cyanoethyl and propionic acid ester groups.
As specific examples of the compounds represented by the above formula (I), there can be mentioned octyl amine, lauryl amine, myristyl amine, palmityl amine, stearyl amine, oleyl amine, behenyl amine and beef tallow amine.
As specific examples of the compounds represented by the above formula (II), there can be mentioned amines prepared by adding acrylonitrile to a higher aliphatic alcohol and reducing the addition product, such as octylaminopropyl ether, 2-ethylhexylaminopropyl ether, laurylaminopropyl ether, myristylaminopropyl ether, stearylaminopropyl ether, oleylaminopropyl ether and behenylaminopropyl ether, and amines prepared by adding ethylene oxide or propylene oxide to a higher aliphatic alcohol or alkyl phenol, then adding acrylonitrile to the terminal hydroxyl group and reducing the addition product. The reason for limiting n to a number not exceeding 20 is that if n is larger than 20, the compatibility with the asphalt is lost. As specific examples of the compounds represented by the formula (III), there can be mentioned amines prepared by adding a compound selected from ethylene oxide, propylene oxide, epichlorohydrin, acrylonitrile and acrylic acid esters to a higher aliphatic diamine, for example, derivatives prepared from higher aliphatic propylene diamines, such as N-octyl-N'-hydroxyethyl propylene diamine, N-lauryl-N'-hydroxyethyl propylene diamine, N-palmityl-N'-hydroxyethyl propylene diamine, N-stearyl-N'-hydroxyethyl propylene diamine, N-oleyl-N'-hydroxyethyl propylene diamine, N-behenyl-N'-hydroxyethyl propylene diamine, N-beef-tallow-N'-hydroxyethyl propylene diamine, N-octyl-N'-1-hydroxy-2-methyl-ethyl propylene diamine, N-lauryl-N'-1-hydroxy-2-methyl-ethyl propylene diamine, N-myristyl-N'-1-hydroxy-2-methyl-ethyl propylene diamine, N-palmityl-N'-1-hydroxy-2-methyl-ethyl propylene diamine, N-stearyl-N'-1-hydroxy-2-methyl-ethyl propylene diamine, N-oleyl-N'-1-hydroxy-2-methyl-ethyl propyl propylene diamine, N-behenyl-N'-1-hydroxy-2-methyl-ethyl propylene diamine, N-beef-tallow-N'-1-hydroxy-2-methyl-ethyl propylene diamine, N-octyl-N'-cyanoethyl propylene diamine, N-lauryl-N'-cyanoethyl propylene diamine, N-myristyl-N'-cyanoethyl propylene diamine, N-palmityl-N'-cyanoethyl propylene diamine, N-stearyl-N'-cyanoethyl propylene diamine, N-oleyl-N'-cyanoethyl propylene diamine, N-behenyl-N'-cyanoethyl propylene diamine, N-beef-tallow-N'-cyanoethyl propylene diamine, N-octyl-N'-methylcarboxyethyl propylene diamine, N-lauryl-N'-methylcarboxyethyl propylene diamine, N-myristyl-N'-methylcarboxyethyl propylene diamine, N-stearyl-N'-methylcarboxyethyl propylene diamine, N-oleyl-N'-methylcarboxyethyl propylene diamine, N-behenyl-N'-methylcarboxyethyl propylene diamine and N-beef-tallow-N'-methylcarboxyethyl propylene diamine, and corresponding derivatives prepared from higher aliphatic ethylene diamines. Since these amines have a good compatibility with asphalts, when they react with compounds having two epoxy groups to form linear polymers, these polymers do not separate from asphalts and homogeneous asphalt-epoxy resin compositions can be obtained.
Resins having two epoxy groups are preferably employed as the epoxy resin in the present invention. For example, there are preferably employed a diglycidyl ether of bisphenol A, a diglycidyl ether of polypropylene glycol, a diglycidyl ether of polyethylene glycol, a diglycidyl ester of phthalic acid, and a diglycidyl ether of a bisphenol A-alkylene oxide adduct.
When a compound having three or more epoxy groups is used and mixed with a heated asphalt, a cross-linked polymer is formed and the composition loses its operational adaptability at once.
Any of the commercially available road-paving asphalts can be used in the present invention but the heating temperature is limited. This limitation is concerned with one of the important features of the present invention, namely, the feature that when the composition of the present invention is used for the paving operation, the road can be opened to traffic immediately after the paving operation. From the viewpoints of cooling and operational adaptability of an asphalt mixture, the time allowed for transportation of the asphalt mixture from the manufacturing plant to the paving position is about 1 hour. It is required that during this period, the epoxy resin should react with the amine and polymerization should be advanced so that when the composition is applied to the road bed and the temperature is lowered to ambient temperature, the road can immediately be opened to traffic. For attaining this feature, in the present invention, the asphalt should be heated to from about 40.degree. to about 250.degree. C.
The grading (particle size) of the aggregate of the asphalt mixture including the composition of the present invention as the binder may be the grading of a customarily used aggregate, but the use of an aggregate having an open grading (large particle size distribution) is preferred. The reason is as follows:
The temperature of an asphalt mixture is considerably reduced while it is being paved and roll-pressed, and the compactness attained by the roll-pressing is therefore often insufficient. This tendency becomes conspicuous as modification of the asphalt progresses. If an aggregate having an open grading, providing large voids in the asphalt mixture, is used, this insufficient compactness can be remarkably moderated.